1. Field of the Invention
The present invention relates to a semiconductor device having a heat spreading layer.
2. Description of the Related Art
In a semiconductor device used in a portable device, downsizing of the semiconductor device is needed. A package called a Chip Size Package (hereinafter, called CSP) has therefore been developed. The CSP is similar in size to a semiconductor chip. A type of CSP is called a wafer level chip size package (Wafer Level Chip Size Package: WCSP) or wafer level chip scale package (Wafer Level Chip Scale Package: WCSP). Such a WCSP is described in Japanese Issued Patent No-3313547.
Recently, portable devices have been operated using a high speed clock. The semiconductor device used in the portable device is operated by a high speed clock. However, as a result of increasing the clock speed, electric power used in the semiconductor chip is increased. Also, as the number of transistors included in the semiconductor chip is increased, the electric power used in the semiconductor device is increased. Since electric power is increased, heat generated by the semiconductor device increases.
For radiating the heat generated by the semiconductor device, a heat radiating part is attached on the semiconductor chip. However, the heat radiating part increases the size of the semiconductor device. That is, the heat radiating part negates the beneficial effect of the WCSP.
A semiconductor device that has an improved heat radiation feature without the use of a heat radiating part has been described in Japanese patent Laid-Open No. 1999-67998. The semiconductor device disclosed in the reference has a film on the surface of the semiconductor device that has a function of heat radiation. However, the reference does not disclose a timing of forming the film. That is, the reference does not consider productivity.